Grooved cylinder liner



May 7, 1957 R. H. SHEPPARD GROOVED CYLINDER LINER Filed May 25, 1955 ENTOR EPPARD lNV fauna H. sa

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GROOVED CYLINDER LINER Richard H. Sheppard, Hanover, Pa.

Application May 25, 1955, Serial No. 511,054

8 Claims. (Cl. 123-493) This invention relates to diesel engines of the type that are at times used at less than full load and has for its principal object the provision of means for preventing deposit of carbon formations upon the piston.

A further object of the invention is the provision of a method and means for preventing blow-by caused by the deposit of carbon on the piston, these deposits tending to form in patches and which as the piston moves in and out will in time form lengthwise or coaxial grooves in the cylinder, such grooves growing deeper until finally a blow-by is formed since the rings on the piston cannot follow or close the grooves.

Where a diesel engine is invariably operated at full load there is never any trouble caused by the formation of so-called carbon which term is used in the trade to refer to the sulfo-carbon ash compounds which are formed in the engine cylinder because in such case the piston which very snugly fits the cylinder or liner will constantly scrape the deposit from the inside surface, thus obviating any possible danger of injuring the liner or cylinder by the formation of elongated axial groovelike marks. Where, however, as is usually the case, the diesel engine must occasionally, and some times for long periods, operate at partial loads, the piston no longer fits the cylinder or liner sufiiciently close to scrape ofi the deposits. The problem is constantly increasing because year by year there is a greater sulfur content of the fuel oil as supplied to diesel engines and this constant increase leads to the increased formation of the sulfo-carbon ash compounds which are deposited either on the piston or on the liner. on the piston itself it is found that these usually form in patches and are rarely uniformly deposited. These patches will move up and down with the piston and scratch the cylinder or liner, the scratches constantly increasing in depth until finally a groove-like mark is formed of such depth that pressure is lost through these axial marks since, obviously, the piston rings are wholly unable to close these scratch marks.

In the drawings:

Figure 1 is an axial section of a liner embodying my invention;

Figure 2 is an axial section much enlarged showing one of the grooves in cross section.

In the drawings the numeral 10 indicates a liner generally or a cylinder for a diesel engine. In the particular form chosen the element 10 is specifically a liner which is intended to be held firmly in place at its head end 11 with its opposite end 12 usually at a lower level free to increase in length when expanded by increased temperature. Near the head end of the cylinder or liner there is formed a plurality of grooves such as 14, 15 and 16 which for a 4 /2 bore would be located, respectively, one-quarter of an inch from the head, a half inch from the head and a trifle less than three-quarters of an inch from the head in the case of groove 16. It is my preference that each groove shall form an equilateral triangle in cross section as shown in Figure 2, the apex When the deposits form United States Patent 2,791,209 Patented May 7, 1957 20 of the groove having a radius of very small size as indicated, thus to prevent the formation of a re-entrant angle which might rise to a crack in the liner or cylinder, a dimension of between four and five hundredths of an inch for the two sides 21 and 22 of the groove giving best results. Since the triangle is equilateral, the angle at 23 will be so that the sharp edge 25 of the groove on either side can readily scrape the piston even at small loads. Diesel pistons have a minimum clearance at heavy loads and consequently the clearance is appreciably greater at lighter loads.

Since the deposit of sulfo-carbon ash compounds, which are very hard, insoluble, and incombustible at any ordinary temperature, is necessarily formed in fuel oils of the types available, it is impossible to avoid the formation of carbon deposits somewhere within the cylinder. When the carbon starts to form on the upper cylindrical surface 26 of the piston, the grooves 14, 15 and 16 will readily shave the carbon formation from this fire-land before it has had a chance to grow in size. The three grooves in the liner provides an anchoring spot for the carbon deposits and hence while the extreme end of the piston is scored, the rings never are.

What I claim is:

l. A diesel engine cylinder having a uniform bore broken only by a plurality of spaced annular grooves at the head end thereof to provide anchoring spaces to receive and hold carbon compounds formed at partial loading of the engine, said grooves being located so as to be covered by the fire-land of the piston when the latter is at top dead center position, whereby the rings of the piston do not come in contact with the grooves.

2. The cylinder of claim 1 in which the grooves are between .04 and .05 inch deep.

3. The cylinder of claim 1 in which the grooves are between .04 and .05 inch wide.

4. The cylinder of claim 1 in which the grooves are all within A" from the head end and are at least three in number.

5. A cylinder liner for a diesel engine, said liner having a plurality of annular grooves at the head end thereof within /2 from the head end and are at least three in number, the grooves being triangular in cross section, each side of the triangle being between .04 and .05 inch, the apex of the triangle being rounded and the two sides from the apex making a sharp margin with the surface of the cylinder to scrape carbon deposits from the snug fitting fire-land of a piston within the liner, said fireland extending in excess of from the head end of the cylinder when the piston is at top dead center position.

6. The method of preventing formation of carbon deposits on the piston of a diesel engine when partially loaded, in which the piston snugly fits the cylinder throughout its entire length when the engine is operating at full load, which consists in forming in a smooth cylindrical surface of the cylinder beyond the first ring of the piston when at top dead center position, an annular depression to receive such deposits, said depression at each side making a sharp angle of about 120 degrees with the radial section of the cylinder.

7. The method of preventing formation of carbon deposits on the piston of a diesel engine when the engine is partially loaded and the piston therefore not in snug contact with the cylinder wall which consists in forming near the head end of the cylinder a plurality of annular grooves located nearer the head end of the cylinder than the distance from the head of the cylinder to the first ring of the piston when the latter is at top dead center position.

8. In an internal combustion engine, a cylinder having a smooth cylindrical bore broken only by a plurality A A -A of spaced annular grooves at the head end and a piston having a smooth outer surface broken by annular grooves to receive the usual piston rings and spaced from the head of the piston by a smooth fire-land of greater axial the piston therefore fits the bore less snugly, and by such removal of carbon spots avoiding scoring of the smooth wall of the bore.

References Cited in the file of this patent UNITED STATES PATENTS Johnson et al. May 1, 1923 Schneider Jan. 19, 1937 Grinham et a1. Jan. 6, 1953 

